Examination of the 12 June 2004 Mulvane, Kansas Tornado

Scott,

Where did you obtain the detail on the Rock tornado track? Did you survey. NSSL sent someone up there afterwards, and couldn't find any damage. He took as many passable back roads and used a GPS and NSSL's Rotation Tracks output, as well as triangulation from our video and vehicle GPS location.
 
Hey Greg,

We were able to plot the Rock, KS tornado track using the video we captured. Eric was east-northeast of the tornado location, whereas I was south of the tornado. This allowed us to observe the movement of the tornado by triangulating both video angles throughout the duration.

View looking north…
http://www.targetarea.net/pic14/jun1204torst2.jpg

View looking west…
http://www.mesoscale.ws/pic2004/040612-24.jpg

The tornado path appeared rather erratic, but had a general motion to the north as the mesocyclone occluded towards the north and finally northwestward. I never heard any official damage reports with the tornado in the sparsely populated region. The tornado was fully condensed during the majority of its duration, so we used the aforementioned video to plot the track. Hope this helps!

Scott Blair
http://www.targetarea.net/
 
Scott,

I concur, a very interesting paper.

The Kansas Turnpike Authority maintains a well-maintained mesonetwork along the Turnpike. There is a station near Belle Plaine and another south of Wellington. WeatherData® archives KTA mesonetwork data at 15 minute intervals. We could provide that data to you if it would helpful.

Mike
 
I am wondering if the cross sectional analysis of this storm showing the lowering of the BWER vault. Is that an example of a Descending Reflectivity Core (DRC) that Dr. Rasmussen is currently studying.
 
Scott, I think this is an interesting read - but a few words of caution regarding your results. First, the characteriszation of the base state environment requires great care - and I wasn't sold on your methodology as shown for how you did this. Correctly calculating theta_x values is important - so folks will want to be sure you measured pressure as well - so showing a pressure trace in your meteogram will add validity. But, most alarming is that your measurements of the 'RFD' are from a distance of ~4 miles, or about 6km - which isn't even in the box shown by the Markowski figure for thermal characteristics in the quadrants around the tornado. You really need closer in observations - and to plot these in a tornado relative framework to make the comparison 'sellable'. If you don't plan to try and formally publish this stuff - you probably have little to worry about - but if you want to take it further feel free to PM me and I'll offer help where I can. Thanks for sharing your work.

Glen
 
Thank you Mike for the data!

As for Jason’s inquiry, the cross sectional analysis we performed with the Mulvane, KS supercell examined the lowering of the BWER. The radar data comes from the WSR-88D in Wichita, KS. The radar site is 20 miles from the tornado, which provides relatively good resolution due to the site within a close proximity of the tornado. However, it does not provide a high temporal or spatial resolution when compared to the DOW data. I’m unaware if the scale of Dr. Rasmussen’s DRC can be truly observed with WSR-88D data as it might require much higher resolution.

The history of observing the descending reflectivity heights associated with the BWER as a potential precursor to tornadogenesis has been documented since the late 1970’s. One excellent paper investigating this is Lemon and Doswell (1979). While I’m unaware of the point of storm origin associated with Dr. Rasmussen’s DRC, I would imagine that these two features (DRC and BWER) could easily be interrelated. Regardless, both of these features independently and together merit further study in the role of tornadogenesis.

Scott Blair
http://www.targetarea.net
 
Hey Glen,

I think I can rest most of your alarms…

First and most importantly, the RFD measurements were taken within 0.25 – 0.8 miles from the tornado, not 4 miles! I’m assuming you were referring to Fig. 12, which the legend reads .2, .3, .4 etc (not whole numbers). The text explains our range from the tornado in great detail, so I’ll refer you to that. The restrictions of publishing this as a conference paper had specific size requirements, therefore the images were scaled down to satisfy those. Secondly, to calculate theta-e and theta-v, pressure is required. And yes, we do have pressure measurements and pressure traces. But again, the restrictions on size for the conference paper limited our ability to include every image created (60+). An alternate form of this paper is already in the works for journal publication, and will include many more images than what is presented here.

The base state storm inflow methodology follows a similar process as Markowski (2002) performed. So, I’m guessing you weren’t sold on Markowski’s methodology. I should point out that Markowski discussed that a normal base state of storm inflow is an arbitrary value; therefore I can see why you might raise issues. However, until a case study will have available a high spatial mobile mesonet network near the tornado and know exactly where each parcel’s origin is arriving, then the BSSI is about as good of a “normal†value we will have to work with.

I hope this helps clarify. Thanks and take care!

Scott Blair
http://www.targetarea.net
 
Thanks Scott for the clarification on the distance scale - it certainly makes a bit difference! That said - what still seems odd is your characterization of the surface inflow environment. No, I don't have a fundamental issue with the bssi methodology, but your cartoon suggests that the inflow to the updraft was restricted to clean air south of the outflow boundary. The surface observation at Winfield KS of 88/73 is certainly warmer than the 79/72 values you sampled behind the tornado - with theta_e deficits seemingly larger than 2K if this were the case. So, you must be basing your surface inflow thermo on the rain-cooled air north of the outflow from the leading convection - but this is not consistent with your cartoon (Fig. 6) - nor the observations you showed. Also, the Fig. 12 is just not as satisfying as if you would redo the plot in tornado relative coordinates so that it would be easier to see where the observations were made relative to the vortex. All we can see is the obs in the one quadrant. I look forward to seeing your later results.

Glen
 
Fig. 6 depicts the location of significant surface boundaries at one time step (0027 UTC). This does not suggest that no other factors contributed to a lower surface temperature inflow value.

To begin, you listed the T/Td of Winfield, KS, approximately 22 miles from the tornado location. This observation is too large of a distance to satisfactorily assume the same thermodynamic conditions exist downstream from the observation site. And in this case, it would have been a fatal assumption.

The two most prominent features we found that lowered the surface temperature of the BSSI from the environment you mentioned 22 miles away was the persistent anvil shadow and the cooler air associated with the left split supercell. The LS1 was the more significant variable as its motion traversed directly across the southeast inflow quadrant of the supercell 10 minutes before and at tornadogenesis before crossing the preexisting outflow boundary. Therefore this likely presented a cooler environment ingested into the mesocyclone than the non-convective sunny sky observation 22 miles away. So no, we did not base any considerations regarding the air mass north of the preexisting outflow boundary when determining the BSSI.

Again, there are more figures than the ones listed in the conference paper. Some figures were time-to-space converted and others contained the raw locations per averaged 30 seconds. Fig. 12 simply served as one example to provide the overview of the thermodynamic and kinematic structure of quadrant 3 in the RFD.

Hope this helps and excellent questions!

Scott Blair
http://www.targetarea.net/
 
Thanks Scott - I think we are getting somewhere here. What it sounds like is that you don't have any observations of what the surface inflow was around the same time that you have observations of the RFD so you chose one that you felt made sense based on the environmental factors (shadowed surface). You also say that assuming the thermodynamic character at Winfield as the inflow would have been a fatal assumption - but I'm baffled as to why you would feel that way. Are you suggesting that if that had been the thermal character of the inflow that the storm could not have produced a tornado?

Next - you contradict yourself in your response - making me even more confused:

Therefore this likely presented a cooler environment ingested into the mesocyclone than the non-convective sunny sky observation 22 miles away

I read inflow not from environment south of boundary. Here is your next sentence:

So no, we did not base any considerations regarding the air mass north of the preexisting outflow boundary when determining the BSSI.

Ok - so if the inflow isn't characterized by the environment north of the boundary, or south of the boundary - what on Earth did you use? I only saw one outflow boundary - is there another we don't see? Best as I can tell - you are assuming the environment sampled by your mobile mesonet ~25 minutes after the tornado as characteristic of the storm inflow at the previous time - but that is a huge assumption - one that would likely never make it through a formal review process.

I know it probably looks like I'm trying to knock your research effort - but that is not my intention at all - I'm just trying to save you some time later by pointing out that there is some work that needs to be done on this to make your argument more concrete. Hopefully the observations that Mike has offered to share may be able to tie things together better.

I'll stop exchanging with you on this now, 'cause I don't want to drag this out indefintely.

Good luck,
Glen
 
Glen,

I’m not exactly sure what is confusing you regarding the methodology and value for the BSSI. But I’ll go ahead and run through this again.

No contradiction whatsoever was made from my previous post. I stated no observations north of the preexisting outflow boundary from downstream convection were considered when determining the BSSI. Yes, obviously observations south of this boundary were considered as I mentioned in the previous post. The observation at Winfield was considered when we determined the BSSI, but not used as face-value to completely represent the true value ingested into the mesocyclone. In addition, we collected data northeast of the mesocyclone and south of the supercell FFD in a narrow region which provided true inflow air within 10 minutes prior to tornadogenesis.

With that being said, two variables 1) anvil shadow 2) left-split supercell south of the preexisting outflow boundary lowered the surface temperature from the observation at Winfield. Previous investigations by Markowski et al. (1997) showed surface temperature decreases of 3°C or more occurred beneath storm anvils compared to the observations outside of the shadow. In this case, if we take the sunny sky Winfield observation of 88°F, and apply this research to this example, the value in the anvil shadow south of the Mulvane tornado is around 82.6°F. The data we collected while in storm inflow prior to tornadogenesis suggested the surface temperature was near 80°F. However, I acknowledged in the paper that some of this air was hypothesized to potentially have mixed with some RFD origin air. Therefore, it was a relatively easy conclusion to define the BSSI ingested at the time of the tornado to be around 82°F.

Glen wrote:
“Are you suggesting that if that had been the thermal character of the inflow that the storm could not have produced a tornado?â€

“Could not have produced†is a tricky statement and one I will avoid using. However, lower LCL heights were present than the observation you mentioned at Winfield. Therefore, I will say it’s a safe assumption that several variables, including the lower surface temperature found with the BSSI, aided in an environment more favorable than the surface environment found at Winfield for tornadogenesis.

Lastly, I should again remind you when Markowski et al. (2002) defined the methodology of the “normal†storm inflow value, he acknowledged the following…
“There is more than one way to estimate the base state (and all techniques are arbitrary and imperfect). It maybe somewhat unconventional to specify a reference state that is not constant in space of time, but the choice is as arbitrary as the decision to make the reference state a constant with respect to space or time. It is believed that what is important is not so much the exact way the base state is specified, but rather that the base state is consistently specified and the differences between the cases are examined.â€

I'm hoping this helped clarify the methodology and value determined for the BSSI. And again, excellent questions! Take care!

Scott Blair
http://www.targetarea.net/
 
I know I said I'd let this go - but I just can't. :)

Therefore, it was a relatively easy conclusion to define the BSSI ingested at the time of the tornado to be around 82°F.

This is manufacturing data - and really is fueled by the misconception that I'll describe below.

Therefore, I will say it’s a safe assumption that several variables, including the lower surface temperature found with the BSSI, aided in an environment more favorable than the surface environment found at Winfield for tornadogenesis.

This is a GCE. Lowering the LCL by cooling the surface inflow alone is not how you make an environment more favorable for tornadoes. If this were the case - tornadoes would be most common in the A.M. when LCL's are typically at their lowest. The value of a lower LCL is that downdrafts entraining air below cloud base will be less susceptible to evaportational cooling when the RH below cloud base is higher. This is meaningless, however, if the surface air has too great of CIN for the dynamic PGF to overcome - forcing the storm to become elevated. The magic of surface boundaries that lead to enhanced threat of tornadogenesis on the cool side are those where the water vapor content on the cool side leads to greater instability despite the lower temperature. Cooling without increase in moisture content does not help the cause.

Lastly, I should again remind you when Markowski et al. (2002) defined the methodology of the “normalâ€￾ storm inflow value, he acknowledged the following…
“There is more than one way to estimate the base state (and all techniques are arbitrary and imperfect). It maybe somewhat unconventional to specify a reference state that is not constant in space of time, but the choice is as arbitrary as the decision to make the reference state a constant with respect to space or time. It is believed that what is important is not so much the exact way the base state is specified, but rather that the base state is consistently specified and the differences between the cases are examined.â€￾

You are using this totally out of context. Let's walk through this and see if you can get a better understanding of what Paul is really saying here. Let's consider two measurements taken in some arbitrary atmospheric state. These measurements can be broken down into the following:

X1 = Xb + X1p

X2 = Xb + X2p

The values X1 and X2 are what we measured, Xb is the background state common to both X1 and X2, and X#p is the perturbation value of X1 and X2 away from the base state. We can break the perturbations down as well to account for instrument error, sampling issues, etc...., but let's just assume for ease of argument that both measurements are perfect. What Markowski is pointing out in his paper about the arbitrary definition of the base state is that we don't really care about the value of Xb - only about the values of the perturbations - because it is the difference in the perturbation values that is important. In Markoswki's examples - samples where taken by mobile mesonets, and he used time to space conversion over I believe were 5 minute intervals - and he argued that over this small time interval this method was acceptable. I concur. The key being the measurements in different quadrants were being sampled simultaneously - not during different stages in the storm's evolution.

Let's apply the above to your study. You have a measurement at X1 (in the RFD) - but no measurement at X2 (in the storm inflow) . Based on the information you have shared, you are trying to assign a value to X2 by approximating Xb and then adding in an X2p based on sampling from another environment. This just isn't a sound methodology. It plays like you are trying to make this case fit the paradigm offered by Markowski - and that tone needs to be played down more and let the data speak for itself.

Glen
 
Glen,

Please read my previous posts a tad more carefully. I indeed have two separate measured X2 values (as mentioned in the previous post) that are found within the “inflow region.â€￾ The data comprised of a certain percentage of sampled air per entire inflow region. However, using either one of these values as an independent representation of the BSSI would cause great misrepresentation when calculating the true state of the BSSI due to the aforementioned variables listed in the previous post. Therefore, using referenced publications that set standards for such situations, the BSSI was determined using both X2 values. If you disagree with this methodology, then you disagree with a large portion of research related to similar situations. The BSSI is an imperfect value and will remain imperfect until mobile mesonet vehicles sample 100% of an interested region. However, some standard must be implemented to examine what data is available and compromise where data is sparse. Markowski et al. (2002) set a fine standard how to accomplish this in such a situation (even when only 10-30% of regions where sampled) and that is what Eric and I accomplished for this paper. The data, methodology, and conclusions speak for itself. As for the comments regarding the LCL height, thanks for not reading carefully. As I mentioned, several variables aided in an environment more favorable than the environment found at Winfield for tornadogenesis. These variables and their role are easily accessible in the paper.

Again, I hope this clarifies any questions you may have. Best of luck to you.

Scott Blair
http://www.targetarea.net/
 
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